<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //用户输入数值
        let num1 = +prompt('输入数值1')
        let num2 = +prompt('输入数值2')
        function sum(a,b) {
            sum=a+b
            return sum   
        }
        let srt = sum(num1,num2)
        document.write(srt)
    </script>
</body>
</html>